Exposure apparatus and device fabrication method

ABSTRACT

A lithographic apparatus includes a substrate table constructed to hold a substrate to be exposed, a projection system configured to project a patterned radiation beam onto a target portion on a side of the substrate to be exposed, a liquid supply system configured to at least partly fill a region between the substrate and the projection system with a liquid, and a liquid confinement structure. The liquid confinement structure is fixed in a plane substantially perpendicular to an optical axis of the projection system and configured to cooperate with the substrate table in order to restrict the liquid to a region above an upper surface of the substrate table so that a side of the substrate to be exposed is substantially covered in the liquid during exposure.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional of U.S. patent application Ser. No. 11/230,572filed Sep. 21, 2005, which in turn is a Continuation of InternationalApplication No. PCT/JP2004/003928, filed Mar. 23, 2004, which claimspriority to Japanese Patent Application No. 2003-83329, filed Mar. 25,2003. The contents of the aforementioned applications are incorporatedherein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus that exposes apattern on a substrate via a projection optical system and a liquid in astate wherein the liquid is filled in at least one part of a spacebetween the projection optical system and the substrate; and a devicefabrication method that uses this exposure apparatus.

2. Description of Related Art

Semiconductor devices and liquid crystal devices are fabricated by aso-called photolithography technique, wherein a pattern formed on a maskis transferred onto a photosensitive substrate.

An exposure apparatus used by this photolithographic process includes amask stage that supports the mask, and a substrate stage that supportsthe substrate, and transfers the pattern of the mask onto the substratevia a projection optical system while successively moving the mask stageand the substrate stage. There has been demand in recent years forhigher resolution projection optical systems in order to handle the muchhigher levels of integration of device patterns. As the exposurewavelength to be used is shorter, the resolution of the projectionoptical system becomes higher. As the numerical aperture of theprojection optical system is larger, the resolution of the projectionoptical system becomes higher. Consequently, the exposure wavelengthused in exposure apparatuses has shortened year by year, and thenumerical aperture of projection optical systems has also increased.Furthermore, the currently mainstream exposure wavelength is the 248 nmKrF excimer laser, but an even shorter wavelength 193 nm ArF excimerlaser is also being commercialized. In addition, as well as resolution,the depth of focus (DOF) is also important when performing an exposure.The following equations respectively express the resolution R and thedepth of focus δ.R=k ₁ ·λ/NA  (1)δ=±k ₂ ·λ/NA ²  (2)

Therein, λ is the exposure wavelength, NA is the numerical aperture ofthe projection optical system, and k₁ and k₂ are the processcoefficients. Equations (1) and (2) teach that, when the exposurewavelength λ is shortened and the numerical aperture NA is increased inorder to enhance the resolution R, then the depth of focus δ isnarrowed.

If the depth of focus δ becomes excessively narrow, then it will becomedifficult to align the surface of the substrate with the image plane ofthe projection optical system, and there will be a risk of insufficientmargin during exposure operation. Accordingly, a liquid immersion methodhas been proposed, as disclosed in, for example, PCT InternationalPublication WO99/49504, as a method to substantially shorten theexposure wavelength and increase the depth of focus. This liquidimmersion method fills a liquid, such as water or an organic solvent,between the lower surface of the projection optical system and thesurface of the substrate, thus taking advantage of the fact that thewavelength of the exposure light in a liquid is 1/n that of in air(where n is the refractive index of the liquid, normally approximately1.2-1.6), thereby improving the resolution as well as increasing thedepth of focus by approximately n times.

Incidentally, inside the chamber of a conventional exposure apparatus(an exposure apparatus for dry exposure), the humidity is lowered and anairflow is generated by an air conditioner, which creates an atmospherein which liquids tend to vaporize. Accordingly, if it is decided toperform immersion exposure in an environment similar to the inside ofthe chamber of the conventional exposure apparatus, then there is apossibility that the liquid for the immersion exposure will vaporize,making it impossible to maintain the control accuracy of the temperatureof that liquid, the projection optical system (a part of the opticalelements) in contact with that liquid, or the substrate. In addition,variations in the temperature of the projection optical system degradethe projected image, and variations in the temperature of the substratedeform (expand and contract) the substrate, creating the possibilitythat the pattern overlay accuracy will degrade.

The present invention has been made considering such circumstances, andhas an object to provide an exposure apparatus and device fabricationmethod capable of accurately forming the image of a pattern on asubstrate when performing the exposure process based on the liquidimmersion method. It is another object of the present invention toprovide an exposure apparatus and device fabrication method capable ofsetting and maintaining at a desired temperature the liquid for liquidimmersion exposure, and a substrate that is to be exposed.

SUMMARY OF THE INVENTION

An exposure apparatus of the present invention is an exposure apparatusthat fills a liquid in at least one part of a space between a projectionoptical system and a substrate, projects the image of a pattern via theprojection optical system and the liquid onto the substrate, and exposesthe substrate, includes a vaporization suppression apparatus thatsuppresses vaporization of the liquid.

In addition, the device fabricating method of the present invention usesthe exposure apparatus as recited above.

According to the present invention, the vaporization suppressionapparatus suppresses the vaporization of the liquid for immersionexposure, and the desired temperature can therefore be set andmaintained by suppressing change in the temperature of the projectionoptical system, the substrate, or the liquid for immersion exposure dueto the vaporization of the liquid. Accordingly, degradation of theprojected image of the projection optical system and deformation of thesubstrate caused by temperature changes can be suppressed, and the imageof the pattern can thereby be formed on the substrate with goodaccuracy.

An exposure apparatus of the present invention is an exposure apparatusthat fills a liquid in at least one part of a space between a projectionoptical system and a substrate, projects the image of a pattern via theprojection optical system and the liquid onto the substrate, and exposesthe substrate, includes a member that forms a closed space thatsurrounds the portion that contacts the liquid; and a vapor pressureadjusting-device to adjust the vapor pressure of the interior of thatclosed space higher than the vapor pressure of the exterior of thatclosed space.

In addition, the device fabricating method of the present invention usesthe exposure apparatus as recited above.

According to the present invention, because of the high vapor pressureof the closed space, which includes the portion that contacts theliquid, the change in the temperature of the portion such as theprojection optical system or the substrate that contacts the liquid, dueto the vaporization of the liquid, is suppressed. Accordingly, the imageof the pattern can thereby be formed on the substrate with goodaccuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram that depicts the first embodiment of anexposure apparatus according to the present invention.

FIG. 2 is an enlarged view of the principal parts in the vicinity of aprojection optical system.

FIG. 3 is a view that depicts an exemplary arrangement of supply nozzlesand collection nozzles.

FIG. 4 is a view that depicts an exemplary arrangement of supply nozzlesand collection nozzles.

FIG. 5 is an enlarged view of the principal parts of the secondembodiment of the exposure apparatus according to the present invention.

FIG. 6 is a flow chart that depicts one example of a semiconductordevice fabrication process.

DETAILED DESCRIPTION OF THE INVENTION

The following explains the preferred embodiments of the presentinvention, referencing the drawings. However, the present invention isnot limited to the embodiments below, e.g., the constituent elements ofthese embodiments may be mutually combined in a suitable manner, andother well-known configurations may be supplemented or substituted.

FIG. 1 is a schematic diagram that depicts the first embodiment of anexposure apparatus EX according to the present invention.

In FIG. 1, the exposure apparatus EX includes a mask stage MST thatsupports a mask M, a substrate stage PST that supports a substrate P, anillumination optical system IL that illuminates with an exposure lightEL the mask M supported by the mask stage MST, a projection opticalsystem PL that projects and exposes a pattern image of the mask Milluminated by the exposure light EL onto the substrate P supported bythe substrate stage PST, and a control apparatus CONT that providesoverall control of the operation of the entire exposure apparatus EX.The exposure apparatus EX of the present embodiment is a liquidimmersion type exposure apparatus that applies the liquid immersionmethod to substantially shorten the exposure wavelength, improve theresolution, as well as substantially increase the depth of focus, andincludes an immersion unit 10 that forms an immersion area AR2 byfilling with a liquid 30 at least one part of a space between theprojection optical system PL and the substrate P.

The immersion unit 10 includes a liquid supply apparatus 1 that suppliesthe liquid 30 onto the substrate P, and a liquid recovery apparatus 2that recovers the liquid 30 on the substrate P. At least during thetransfer of the pattern image of the mask M onto the substrate P, theexposure apparatus EX forms the immersion area AR2 of the liquid 30supplied from the liquid supply apparatus 1, in one part on thesubstrate P that includes a projection area AR1 of the projectionoptical system PL. Specifically, the exposure apparatus EX fills thespace between an optical element PLa of the tip part of the projectionoptical system PL and the surface of the substrate P with the liquid 30;projects the pattern image of the mask M onto the substrate P via theliquid 30 between the optical element PLa of this projection opticalsystem PL and the substrate P, and via the projection optical system PL;and exposes the substrate P. Furthermore, the exposure apparatus EXincludes a vaporization suppression unit 20 that constitutes at leastone part of a vaporization suppression apparatus that suppresses thevaporization of the liquid 30, which is discussed in detail later.

The present embodiment will now be explained as exemplified by a case ofthe use of the scanning type exposure apparatus (so-called scanningstepper) as the exposure apparatus EX in which the substrate P isexposed with the pattern formed on the mask M while synchronously movingthe mask M and the substrate P in mutually different directions(opposite directions) in the scanning directions. In the followingexplanation, the direction that coincides with an optical axis AX of theprojection optical system PL is the Z axial direction, the direction inwhich the mask M and the substrate P synchronously move in the planeperpendicular to the Z axial direction (the scanning direction) is the Xaxial direction, and the direction perpendicular to the Z axialdirection and the Y axial direction is the Y axial direction (thenon-scanning direction). In addition, the directions around the X, Y,and Z-axes are the θX, θY, and θZ directions. Herein, “substrate”includes one in which a semiconductor wafer is coated with aphotoresist, which is a photosensitive material, and “mask” includes areticle formed with a device pattern subject to the reduction projectiononto the substrate.

The illumination optical system IL illuminates with the exposure lightEL the mask M supported by the mask stage MST, and includes an exposurelight source, an optical integrator that uniformizes the intensity ofthe luminous flux emitted from the exposure light source, a condenserlens that condenses the exposure light EL from the optical integrator, arelay lens system, and a variable field stop that sets an illuminationregion on the mask M illuminated by the exposure light EL to beslit-shaped, and the like. The illumination optical system ILilluminates the prescribed illumination region on the mask M with theexposure light EL, having a uniform illumination intensity distribution.Those usable as the exposure light beam EL radiated from theillumination optical system IL include, for example, bright lines(g-ray, h-ray, i-ray) in the ultraviolet region radiated, for example,from a mercury lamp, far ultraviolet light beams (DUV light beams) suchas the KrF excimer laser beam (wavelength: 248 nm), and vacuumultraviolet light beams (VUV light beams) such as the ArF excimer laserbeam (wavelength: 193 nm) and the F₂ laser beam (wavelength: 157 nm).ArF excimer laser light is used in the present embodiment.

The mask stage MST supports the mask M, and is two dimensionally movablein the plane perpendicular to the optical axis AX of the projectionoptical system PL, i.e., in the XY plane, and is finely-rotatable in theθZ direction. A mask stage drive apparatus MSTD, includes a linear motorand the like, drives the mask stage MST. The control apparatus CONTcontrols the mask stage drive apparatus MSTD. A movable mirror 50 isprovided on the mask stage MST. In addition, a laser interferometer 51is provided at a position opposing the movable mirror 50. The laserinterferometer 51 measures in real time the position, in the twodimensional direction, and the rotational angle of the mask M on themask stage MST, and outputs the measurement results to the controlapparatus CONT. The control apparatus CONT drives the mask stage driveapparatus MSTD based on the measurement results of the laserinterferometer 51, thereby positioning the mask M, which is supported bythe mask stage MST.

The projection optical system PL projects and exposes the pattern of themask M onto the substrate P with a predetermined projectionmagnification β. The projection optical system PL includes a pluralityof optical elements, including the optical element (lens) PLa providedat the tip part on the substrate P side. These optical elements aresupported by a lens barrel PK. In the present embodiment, the projectionoptical system PL is a reduction system having a projectionmagnification β of, for example, ¼ or ⅕. The projection optical systemPL may be either a unity magnification system or an enlargement system.In addition, the optical element PLa of the tip part of the projectionoptical system PL of the present embodiment is attachably and detachably(replaceably) provided to and from the lens barrel PK, and the liquid 30that forms the immersion area AR2 contacts the optical element PLa.

The substrate stage PST supports the substrate P. The substrate stagePST includes a Z stage 52 that holds the substrate P via a substrateholder, and an XY stage 53 that supports the Z stage 52. Further, a base54 supports the XY stage 53 of this substrate stage PST. A substratestage drive apparatus PSTD includes a linear motor and the like, drivesthe substrate stage PST. The control apparatus CONT controls thesubstrate stage drive apparatus PSTD. Driving the Z stage 52 controlsthe position in the Z axial direction (the focus position) and in the θXand θY directions of the substrate P held on the Z stage 52. Inaddition, driving the XY stage 53 controls the position of the substrateP in the XY direction (the position in a direction substantiallyparallel to the image plane of the projection optical system PL). Inother words, the Z stage 52 controls the focus position and theinclination angle of the substrate P and aligns the surface of thesubstrate P with the image plane of the projection optical system PL inan auto-focus manner and an auto-leveling manner. Further, the XY stage53 positions the substrate P in the X axial direction and Y axialdirection. Furthermore, the Z stage and the XY stage may be integrallyprovided. A movable mirror 55 is provided on the substrate stage PST(the Z stage 52). In addition, a laser interferometer 56 is provided ata position opposing the movable mirror 55. The laser interferometer 56measures in real time the position in the two dimensional direction andthe rotational angle of the substrate P on the substrate stage PST, andoutputs the measurement results to the control apparatus CONT. Thecontrol apparatus CONT drives the substrate stage drive apparatus PSTDbased on the measurement results of the laser interferometer 56, therebypositioning the substrate P supported on the substrate stage PST.

The liquid supply apparatus 1 of the immersion unit 10 fills with theliquid 30 at least one part of the space between the projection opticalsystem PL and the substrate P by supplying the prescribed liquid 30 ontothe substrate P. The liquid supply apparatus 1 includes a tank thataccommodates the liquid 30, a filter that eliminates foreign matter fromthe liquid 30, a pressure pump, and the like. Furthermore, the liquidsupply apparatus 1 includes a temperature adjusting-device that adjuststhe temperature of the liquid 30 supplied onto the substrate P. Thetemperature adjusting-device adjusts the temperature of the liquid 30 tobe supplied to substantially the same level as, for example, thetemperature of the space inside the chamber apparatus housed by theexposure apparatus EX. One end of a supply pipe 3 is connected to theliquid supply apparatus 1, and a supply nozzle 4 is connected to theother end of the supply pipe 3. The supply nozzle 4 is disposed close tothe substrate P, and the liquid supply apparatus 1 supplies the liquid30 between the projection optical system PL and the substrate P via thesupply pipe 3 and the supply nozzle 4. In addition, the controlapparatus CONT controls the operation of supplying the liquid of theliquid supply apparatus 1, and can control the liquid supply amount perunit time of the liquid supply apparatus 1.

In the present embodiment, pure water is used as the liquid 30. Purewater is capable of transmitting not only ArF excimer laser light, butalso deep ultraviolet light (DUV light), such as the bright lines (g, h,and i lines) in the ultraviolet region emitted from, for example, amercury lamp, and KrF excimer laser light (248 nm wavelength).

The liquid recovery apparatus 2 recovers the liquid 30 on the substrateP, and includes a suction apparatus, such as, for example, a vacuumpump, a tank that accommodates the recovered liquid 30, and the like.One end of a recovery pipe 6 is connected to the liquid recoveryapparatus 2, and a recovery nozzle 5 is connected to the other end ofthe recovery pipe 6. The recovery nozzle 5 is disposed close to thesubstrate P, and the liquid recovery apparatus 2 recovers the liquid 30via the recovery nozzle 5 and the recovery pipe 6. In addition, thecontrol apparatus CONT controls the operation of recovering the liquidby the liquid recovery apparatus 2, and can control the liquid recoveryamount per unit time of the liquid recovery apparatus 2.

The control apparatus CONT drives the liquid supply apparatus 1 tosupply a predetermined amount of liquid 30 per unit of time on thesubstrate P via the supply pipe 3 and the supply nozzle 4, and drivesthe liquid recovery apparatus 2 to recover a predetermined amount ofliquid 30 per unit of time from on the substrate P via the recoverynozzle 5 and the recovery pipe 6. Thereby, the liquid 30 is disposedbetween the tip part PLa of the projection optical system PL and thesubstrate P, forming the immersion area AR2.

The vaporization suppression unit 20 suppresses the vaporization of theliquid 30 by setting the space surrounding the liquid 30 higher than apredetermined vapor pressure. This vaporization suppression unit 20includes a partition member 21 that encloses the space surrounding theliquid 30 between the projection optical system PL and the substrate P,and a humidifier 28 that constitutes at least one part of a supplyapparatus that supplies vapor to a closed space 24, which is formed bythe partition member 21 and includes the space surrounding the liquid30. The partition member 21 includes a wall member 22 affixed to thevicinity of a circumferential edge part of the substrate stage PST (Zstage 52) so that it encloses the substrate P, and having a wall surfaceof a predetermined height; and a cover 23 affixed to the lens barrel PKof the projection optical system PL, and having a lower surfacesubstantially parallel to the XY plane and of a predetermined size. Thecover 23 may be affixed to a support member (not shown) that supportsthe projection optical system PL (lens barrel PK). The wall member 22and the cover 23 that constitute the partition member 21 form the closedspace 24 that encloses the substrate P and the liquid 30 between theprojection optical system PL and the substrate P. A small gap 25 isformed between an upper end part of the wall member 22 and the lowersurface of the cover 23 so that the movement of the substrate stage PSTin the X, Y, and Z axial directions and the inclination of the substratestage PST are not interfered. In addition, through holes through whichthe supply pipe 3 and the recovery pipe 6 can be respectively disposedare provided in one part of the cover 23. Sealing members (not shown)are provided that each restrict the flow of liquid through the gapbetween the through holes and the respective supply pipe 3 andcollection pipe 6.

A through hole 26 is formed in one part of the wall member 22 providedon the substrate stage PST, and one end of an elastically providedpiping 27 is connected to this through hole 26. Meanwhile, thehumidifier 28 that supplies vapor to the closed space 24 is connected tothe other end of the piping 27. The humidifier 28 supplies high humiditygas to the closed space 24 via the piping 27, and supplies a vapor ofthe same substance as the liquid 30. In the present embodiment, theliquid 30 is water (pure water), so the humidifier 28 supplies watervapor to the closed space 24. The control apparatus CONT controls thevapor supply operation of the humidifier 28. Furthermore, by supplyingvapor to the closed space 24 using the humidifier 28, the vaporizationsuppression unit 20 raises the vapor pressure (pressure in the vaporphase) in the closed space 24 on the inner side of the partition member21 higher than the outer side thereof (i.e., the interior of the chamberapparatus).

FIG. 2 is a front view that depicts the vicinity of the tip part of theprojection optical system PL of the exposure apparatus EX. The tip partof the optical element PLa at the lowest end of the projection opticalsystem PL is formed in a long, thin rectangular shape in the Y axialdirection (the non-scanning direction), leaving just the portion neededin the scanning direction. During scanning exposure, the pattern imageof one part of the mask M is projected onto the rectangular projectionarea AR1 directly below the optical element PLa, and, synchronized tothe movement of the mask M at a speed V in the −X direction (or the +Xdirection) with respect to the projection optical system PL, thesubstrate P moves at a speed β·V (where β is the projectionmagnification) in the +X direction (or the −X direction) via the XYstage 53. Further, after the exposure of one shot region is completed,the next shot region moves to the scanning start position by thestepping movement of the substrate P, and the exposure process issubsequently performed sequentially for each shot region by thestep-and-scan system. In the present embodiment, the liquid 30 is set sothat it flows parallel to and in the same direction as the movementdirection of the substrate P.

FIG. 3 depicts the positional relationship between the projection areaAR1 of the projection optical system PL, the supply nozzles 4 (4A-4C)that supply the liquid 30 in the X axial direction, and the recoverynozzles 5 (5A, 5B) that recover the liquid 30. In FIG. 3, the projectionarea AR1 of the projection optical system PL is a rectangular shape thatis long and thin in the Y axial direction. Further, the three supplynozzles 4A-4C are disposed on the +X direction side and the two recoverynozzles 5A, 5B are disposed on the −X direction side so that theprojection area AR1 is interposed therebetween in the X axial direction.The supply nozzles 4A-4C are connected to the liquid supply apparatus 1via the supply pipe 3, and the recovery nozzles 5A, 5B are connected tothe liquid recovery apparatus 2 via the recovery pipe 6. In addition,supply nozzles 8A-8C and recovery nozzles 9A, 9B are disposed in anarrangement substantially 180° rotated from the supply nozzles 4A-4C andthe recovery nozzles 5A, 5B. The supply nozzles 4A-4C and the recoverynozzles 9A, 9B are alternately arrayed in the Y axial direction, thesupply nozzles 8A-8C and the recovery nozzles 5A, 5B are alternatelyarrayed in the Y axial direction, the supply nozzles 8A-8C are connectedto the liquid supply apparatus 1 via a supply pipe 11, and the recoverynozzles 9A, 9B are connected to the liquid recovery apparatus 2 via arecovery pipe 12.

The following explains the procedure for using the exposure apparatus EXdiscussed above to expose the pattern of the mask M onto the substrateP.

After the mask M is loaded on the mask stage MST and the substrate P isloaded on the substrate stage PST, the control apparatus CONT drives theliquid supply apparatus 1 and the liquid recovery apparatus 2 of theimmersion unit 10, and forms the immersion area AR2 between theprojection optical system PL and the substrate P. In addition, thecontrol apparatus CONT drives the humidifier 28 of the vaporizationsuppression unit 20, thereby supplying vapor to the closed space 24 thatincludes the surrounding space of liquid 30 that is formed by theimmersion area AR2, thereby the vapor phase pressure of this closedspace 24 becomes higher than a predetermined vapor pressure.Specifically, by supplying the water vapor, which is a high humiditygas, to the closed space 24, the vaporization suppression unit 20 setsthis closed space 24 to the saturated vapor pressure of the liquid (purewater) 30.

The vapor pressure of the closed space 24 rises higher than the vaporpressure on the outside of the closed space 24. Normally, the humidityon the outside of the closed space 24, i.e., inside the chamber thathouses the exposure apparatus EX, is 30%-40%, but the interior of thespace 24 is constantly maintained near the saturated vapor pressure(approximately 95% humidity) because the humidifier 28 of thevaporization suppression unit 20 is continuously supplying water vapor.It is possible to maintain the interior of the space 24 near thesaturated vapor pressure because the gap 25 provided between the upperend part of the wall member 22 and the cover 23 is extremely small.

If scanning exposure is performed by moving the substrate P in thescanning direction (the −X direction) depicted by an arrow Xa (refer toFIG. 3), then the liquid supply apparatus 1 and the liquid recoveryapparatus 2 use the supply pipe 3, the supply nozzles 4A-4C, therecovery pipe 6, and the recovery nozzles 5A, 5B to supply and recoverthe liquid 30. On the other hand, if scanning exposure is performed bymoving the substrate P in the scanning direction (the +X direction)depicted by an arrow Xb, then the liquid supply apparatus 1 and theliquid recovery apparatus 2 use the supply pipe 11, the supply nozzles8A-8C, the recovery pipe 12, and the recovery nozzles 9A, 9B to supplyand recover the liquid 30. Thus, the immersion unit 10 uses the liquidsupply apparatus 1 and the liquid recovery apparatus 2 to flow theliquid 30 along the direction of movement of the substrate P and in adirection the same as the direction of movement of the substrate P. Inthis case, the liquid 30 can be easily supplied between the projectionoptical system PL and the substrate P, even if the supplied energy ofthe liquid supply apparatus 1 is small, because the liquid 30 supplied,for example, from the liquid supply apparatus 1 via the supply nozzles4A-4C flows so that it is drawn between the projection optical system PLand the substrate P as the substrate P moves in the −X direction.Further, even if the substrate P is scanned in either the +X directionor the −X direction by switching the direction in which the liquid 30flows in accordance with the scanning direction, the liquid 30 can befilled between the projection optical system PL and the substrate P, anda high resolution and large depth of focus can thereby be obtained. Inaddition, because the minute gap 25 is provided between the upper endpart of the wall member 22 and the cover 23, the substrate stage PST canalso be moved while maintaining the inside of the closed space 24 nearthe saturated vapor pressure.

As explained above, the partition member 21 forms the closed space 24surrounding the substrate P and the liquid 30 that forms the immersionarea AR2, and water vapor is supplied inside this closed space 24;therefore, the vaporization of the liquid 30 and of the liquid 30adhering to the tip part of the projection optical system PL and thesubstrate P can be suppressed, and the liquid 30, the projection opticalsystem PL, and the substrate P can be maintained at the desiredtemperature. In particular, if an immersion area is formed on one partof the substrate P while recovering the liquid on the substrate P, then,even if the un-recovered residual liquid adheres to the substrate P, thevaporization of that residual liquid can be prevented, and it ispossible to suppress temperature changes and deformations (expansion andcontraction) of the substrate P. In addition, even if liquid adheres tothe side surfaces of the optical element PLa of the projection opticalsystem PL, the vaporization of that adhered liquid can be prevented,thereby enabling the suppression of temperature changes and deformationof the optical element PLa.

In the present embodiment, the movable mirror 55 affixed to thesubstrate stage PST is provided on the outside of the closed space 24,and the measurement of the position of the substrate stage PST by theinterferometer 56 using the movable mirror 55 is consequently notaffected by the environment inside the closed space 24. In addition,because water vapor of pure water the same as the liquid (pure water) 30is supplied to the closed space 24 to humidify the closed space 24,there is no drop in the purity of the liquid (pure water) 30 between theprojection optical system PL and the substrate P, nor any change in thetransmittance or other characteristics.

In the present embodiment, the vapor supplied to the closed space 24 hasthe same physical properties as the liquid 30 that forms the immersionarea AR2. However, if deterioration in the purity of the liquid 30between the projection optical system PL and the substrate P ispermissible to some extent, then the physical properties of the liquid30 supplied from the liquid supply apparatus 1 for forming the immersionarea AR2 need not be the same as those of the vapor supplied inside theclosed space 24.

In the present embodiment, the interior of the closed space 24 is set tosubstantially the saturated vapor pressure (approximately 95% humidity),but may be set lower than that, e.g., approximately 60%. In other words,the pressure of the vapor phase of the closed space 24 may be set to apredetermined vapor pressure that is lower than the saturated vaporpressure. Here, the predetermined vapor pressure is a pressure whereinfluctuations in the pattern transfer accuracy due to temperaturefluctuations in the tip part of the projection optical system PL, thesubstrate P, or the liquid 30 caused by vaporization of the liquid 30can be kept within a permissible range. Accordingly, by setting thespace surrounding the liquid 30 for forming the immersion area AR2higher than the predetermined vapor pressure with the aid of thevaporization suppression unit 20, the pattern transfer accuracy can bekept within the permissible range.

Although the liquid 30 in the present embodiment is water (pure water),it may be a liquid other than water. For example, if the light source ofthe exposure light EL is an F₂ laser, then this F₂ laser light will nottransmit through water, so it would be acceptable to use as the liquid30 a fluorine based liquid, such as fluorine based oil, capable oftransmitting the F₂ laser light (e.g., Fomblin® and PFPE). In that case,the vapor of the fluorine based liquid is supplied to the spacesurrounding the substrate P (the closed space 24). If a fluorine basedliquid is used for the immersion exposure, then a substance the same asthat liquid may be vaporized, and that vapor may be supplied inside theclosed space 24. In addition, it is also possible to use, as the liquid30, those (e.g., cedar oil) that is transparent to the exposure lightEL, has the highest possible refractive index, and is stable withrespect to the projection optical system PL and the photoresist coatedon the surface of the substrate P.

In either case, vapor having physical properties the same as thatliquid, or a vapor having a chemical composition the same as the vaporproduced by vaporizing that liquid may be supplied to the spacesurrounding the substrate P (the closed space 24).

The above embodiments are not particularly limited to the nozzleconfigurations discussed above, e.g., the liquid 30 may be supplied andrecovered by two pairs of nozzles on the long sides of the projectionarea AR1 of the projection optical system PL. In this case, the supplynozzles and the recovery nozzles may be disposed so that they arearrayed vertically in order to enable the supply and recovery of theliquid 30 from either the +X direction or the −X direction.

In addition, as shown in FIG. 4, supply nozzles 41, 42 and recoverynozzles 43, 44 may also be provided respectively on both sides in the Yaxial direction, wherebetween the projection area AR1 of the projectionoptical system PL is interposed. These supply nozzles and recoverynozzles can stably supply the liquid 30 between the projection opticalsystem PL and the substrate P, even when the substrate P is moving inthe non-scanning direction (the Y axial direction) during the steppingmovement. In addition, if the liquid 30 supply nozzles and recoverynozzles are provided so that they surround the projection area AR1 ofthe projection optical system PL, then it is possible also to switch thedirection in which the liquid 30 flows in response to the movementdirection of the substrate P at times such as when the substrate P isbeing stepped in the Y axial direction.

The following explains the second embodiment of the exposure apparatusEX according to the present invention, referencing FIG. 5. In theexplanation below, constituent parts that are identical or equivalent tothose in the first embodiment discussed above are assigned the identicalreference characters, and the explanation thereof is simplified oromitted.

In FIG. 5, the vaporization suppression unit 20 includes a partitionmember 60 affixed onto the base 54. In other words, the partition member21 according to the abovementioned first embodiment includes the wallmember 22 and the cover 23, and forms a gap 25, but there is no gap inthe partition member 60 according to the present embodiment, and aclosed space 61 formed by this partition member 60 is an approximatelysealed closed space. In this case, the substrate stage PST moves insidethe closed space 61 on the base 54. By making the closed space 61 anapproximately sealed closed space, it is that much easier to maintainthe interior of this closed space 61 near the saturated vapor pressureof the liquid 30, and the impact on the outside of the closed space 61can be eliminated. Here, if the measurement light of the interferometerused to measure the position of the substrate stage PST passes throughthe interior of the closed space 61, then a tubular member canelastically cover the optical path of the measurement light so that thevapor inside the closed space 61 does not impact the measurementoperation.

The abovementioned first and second embodiments are configured so thatthe space surrounding the substrate P and the liquid 30 for forming theimmersion area AR2 are made a closed space, and so that vapor issupplied into this closed space. However, it is also acceptable tosuppress the vaporization of the liquid 30 for forming the immersionarea AR2 by simply blowing the vapor to the space surrounding the liquid30 (to the vicinity of the tip part of the projection optical system PL,and to the vicinity of the surface of the substrate P), without formingthe closed space. In this case, the same as discussed above, the opticalpath (luminous flux) of the interferometer may be covered by the tubularmember so that the vapor does not affect the interferometer'smeasurements.

In addition, in the first and second embodiments discussed above, ahumidity sensor may be disposed inside the closed spaces 24, 61, and thehumidifier 28 may be controlled based on the output of that humiditysensor.

In addition, after the exposure of the substrate P is completed, thevapor pressure inside the closed spaces 24, 61 is made substantially thesame as the vapor pressure of the space on the outside of the closedspaces 24, 61, after which the substrate P may be transported out of theclosed spaces 24, 61.

In the abovementioned first and second embodiments, a humidifier 28 isprovided that supplies vapor to the interior of the closed spaces 24,61, but it is also acceptable to omit this. In other words, even if onlyforming the closed spaces 24, 61, the vaporization of the liquid can besuppressed because the liquid that contacts (adheres to) the substrate Pand the vicinity of the tip of the projection optical system PL can beprotected from contact with the dried air inside the chamber that housesthe apparatus, or the airflow inside the chamber.

In addition, the abovementioned first and second embodiments suppressthe vaporization of the liquid by forming the closed spaces 24, 61, butit is also acceptable to blow a high vapor pressure (high humidity)vapor toward the vicinity of the tip of the projection optical system PLand the surface of the substrate P, without providing the partitionmembers 21, 60.

In addition, the present invention is not limited to the large closedspaces 24, 61 such as in the first and second embodiments, and a localclosed space may be provided so that it encloses the portion that makescontact with (adheres to) the liquid.

As discussed above, the liquid 30 in the present embodiment includespure water. Pure water is advantageous because it can be easily obtainedin large quantities at a semiconductor fabrication plant, and the like.Further, because pure water has no adverse impact on the optical element(lens), the photoresist on the substrate P, and the like. In addition,because pure water has no adverse impact on the environment and has anextremely low impurity content, it can also be expected to have theeffect of cleaning the surface of the substrate P, and the surface ofthe optical element provided on the tip surface of the projectionoptical system PL. Further, because the refractive index n of pure water(water) for the exposure light EL having a wavelength of approximately193 nm is substantially 1.44, the use of ArF excimer laser light (193 nmwavelength) as the light source of the exposure light EL would shortenthe wavelength on the substrate P to 1/n, i.e., approximately 134 nm,thereby obtaining a high resolution. Furthermore, because the depth offocus will increase approximately n times, i.e., approximately 1.44times, that of in air, the numerical aperture of the projection opticalsystem PL can be further increased if it is preferable to ensure a depthof focus approximately the same as that when used in air, and theresolution is also improved from this standpoint.

In each of the abovementioned embodiments, a lens is affixed as theoptical element PLa at the tip of the projection optical system PL, andthe optical characteristics of the projection optical system PL, e.g.,aberrations (spherical aberration, coma aberration, and the like) can beadjusted by this lens. The optical element PLa may also be an opticalplate that adjusts the above optical characteristics. Further, theoptical element PLa that contacts the liquid 30 can also be a planeparallel plate lower in cost than the lens. Using a plane parallel plateas the optical element PLa is advantageous because, even if a substance(e.g., a silicon based organic substance, and the like) that lowers theuniformity of the transmittance of the projection optical system PLduring the transport, assembly, and adjustment of the exposure apparatusEX, and the illumination intensity and the illumination intensitydistribution of the exposure light EL on the substrate P adheres to thatplane parallel plate, only the plane parallel plate needs to be replacedimmediately before supplying the liquid, and that replacement cost islower than that compared with using a lens as the optical element thatcontacts the liquid. In other words, because the surface of the opticalelement that contacts the liquid becomes contaminated because of theadhesion of scattered particles generated from the resist due to theirradiation of the exposure light EL, and because of impurities in theliquid, and the like, that optical element must be periodicallyreplaced. However, by using a low cost plane parallel plate for thisoptical element, the cost of the replacement part is lower compared witha lens, less time is needed to effect the replacement, and it ispossible to suppress any increase in the maintenance cost (running cost)or decrease in throughput.

If a high pressure is generated by the flow of the liquid between thesubstrate P and the optical element PLa at the tip of the projectionoptical system PL, then instead of making the optical elementreplaceable, the optical element may be firmly fixed by that pressure sothat it does not move.

Each of the abovementioned embodiments is constituted so that the liquidis filled between the projection optical system PL and the surface ofthe substrate P, but may be constituted so that the liquid is filled ina state wherein, for example, a cover glass comprising a plane parallelplate is affixed to the surface of the substrate P.

The substrate P in each of the above-mentioned embodiments is notlimited to a semiconductor wafer for fabricating semiconductor devices,and is also applicable to a glass substrate for a display device, aceramic wafer for a thin film magnetic head, or a mask or the originalplate of a reticle (synthetic quartz, silicon wafer) used by an exposureapparatus, and the like.

In addition to a step-and-scan system scanning type exposure apparatus(scanning stepper) that scans and exposes the pattern of the mask M bysynchronously moving the mask M and the substrate P, a step-and-repeatsystem projection exposure apparatus (stepper) that exposes the fullpattern of the mask M with the mask M and the substrate P in astationary state is also applicable as the exposure apparatus EX. Inaddition, the present invention is also applicable to a step-and-stitchsystem exposure apparatus that partially and superimposingly transfersat least two patterns onto the substrate P.

In the embodiments discussed above, an exposure apparatus is used thatlocally fills liquid between the projection optical system PL and thesubstrate P, but the present invention is also applicable to a liquidimmersion exposure apparatus that moves a stage, which holds thesubstrate to be exposed, in a liquid bath, as disclosed in JapaneseUnexamined Patent Application, First Publication No. H06-124873, as wellas to a liquid immersion exposure apparatus that forms a liquid bathhaving a predetermined depth on the stage, and holding the substratetherein, as disclosed in Japanese Unexamined Patent Application, FirstPublication No. H10-303114.

In addition, the present invention is also applicable to twin-stage typeexposure apparatuses as disclosed in Japanese Unexamined PatentApplications, First Publication No. H10-163099 and No. H10-214783, andPublished Japanese Translation No. 2000-505958 of the PCT InternationalPublication.

The type of exposure apparatus EX is not limited to semiconductor devicefabrication exposure apparatuses that expose the pattern of asemiconductor device on the substrate P, but is also widely applicableto exposure apparatuses for fabricating liquid crystal devices ordisplays, exposure apparatuses for fabricating thin film magnetic heads,imaging devices (CCD), or reticles and masks, and the like.

If a linear motor is used in the substrate stage PST or the mask stageMST (refer to U.S. Pat. No. 5,623,853 and U.S. Pat. No. 5,528,118), theneither an air levitation type that uses an air bearing or a magneticlevitation type that uses Lorentz's force or reactance force may beused. In addition, each of the stages PST, MST may be a type that movesalong a guide, or may be a guideless type not provided with a guide.

For the drive mechanism of each of the stages PST, MST, a planar motormay be used that opposes a magnet unit wherein magnets are arranged twodimensionally to an armature unit wherein coils are arranged twodimensionally, and drives each of the stages PST, MST by electromagneticforce. In this case, any one among the magnet unit and the armature unitis connected to the stages PST, MST, and the other one of the magnetunit and the armature unit should be provided on the moving surface sideof the stages PST, MST.

The reaction force generated by the movement of the substrate stage PSTmay be mechanically discharged to the floor (ground) using a framemember so that it is not transmitted to the projection optical systemPL, as recited in Japanese Unexamined Patent Application, FirstPublication No. H08-166475 (U.S. Pat. No. 5,528,118).

The reaction force generated by the movement of the mask stage MST maybe mechanically discharged to the floor (earth) using a frame member sothat it is not transmitted to the projection optical system PL, asrecited in Japanese Unexamined Patent Application, First Publication No.H08-330224 (U.S. Pat. No. 5,528,118).

The exposure apparatus EX of the embodiments in the present applicationas described above is manufactured by assembling various subsystems,including each constituent element recited in the claims of the presentapplication, so that a predetermined mechanical accuracy, electricalaccuracy, and optical accuracy are maintained. To ensure these variousaccuracies, adjustments are performed before and after this assembly,including an adjustment to achieve optical accuracy for the variousoptical systems, an adjustment to achieve mechanical accuracy for thevarious mechanical systems, and an adjustment to achieve electricalaccuracy for the various electrical systems. The assembly process, fromthe various subsystems to the exposure apparatus includes the mutualmechanical connection of the various subsystems, the wiring andconnection of electrical circuits, the piping and connection of theatmospheric pressure circuit, and the like. Naturally, before theprocess of assembling from these various subsystems to the exposureapparatus, there are processes for assembling each of the individualsubsystems. When the assembly process from various subsystems to theexposure apparatus has completed, a comprehensive adjustment isperformed to ensure the various accuracies of the exposure apparatus asa whole. It is preferable to manufacture the exposure apparatus in aclean room wherein the temperature, the cleanliness level, and the like,are controlled.

As shown in FIG. 6, a micro-device, such as a semiconductor device ismanufactured by: a step 201 that designs the functions and performanceof the micro-device; a step 202 that fabricates a mask (reticle) basedon this design step; a step 203 that fabricates a substrate, which isthe base material of the device; an exposure processing step 204 whereinthe exposure apparatus EX of the embodiments discussed above exposes apattern of the mask onto the substrate; a device assembling step 205(comprising a dicing process, a bonding process, and a packagingprocess); a scanning step 206; and the like.

1. A lithographic apparatus, comprising: a substrate table constructedto hold a substrate to be exposed; a projection system configured toproject a patterned radiation beam onto a target portion on a side ofthe substrate to be exposed; a liquid supply system configured to atleast partly fill a region between the substrate and the projectionsystem with a liquid; and a liquid confinement structure fixed in aplane substantially perpendicular to an optical axis of the projectionsystem and configured to cooperate with the substrate table in order torestrict the liquid to a region above an upper surface of the substratetable so that a side of the substrate to be exposed is substantiallycovered in the liquid during exposure.
 2. The apparatus according toclaim 1, wherein a portion of the liquid confinement structure extendsfurther towards the substrate than any part of a final element of theprojection system.
 3. The apparatus according to claim 1, wherein thesubstrate table comprises: a substrate seat configured to hold thesubstrate; and a sealing projection surrounding the substrate seat in aplane substantially perpendicular to the optical axis and configured tocooperate with the liquid confinement structure so as to substantiallyprevent liquid from escaping from the region between the substrate andthe projection system.
 4. The apparatus according to claim 3, whereinthe sealing projection comprises a gas seal configured to substantiallyprevent flow of liquid through a gap between a surface of the liquidconfinement structure and the sealing projection.
 5. The apparatusaccording to claim 4, wherein the gas seal is arranged to produce a flowof gas within the gap that is directed substantially towards the opticalaxis in such a way as to at least partially confine the liquid.
 6. Theapparatus according to claim 1, wherein: the liquid confinementstructure comprises a gas seal, and the substrate table comprises asealing zone arranged to cooperate with the gas seal so as tosubstantially prevent liquid from escaping from the region between thesubstrate and the projection system.
 7. A lithographic apparatus,comprising: a projection system configured to project a patternedradiation beam onto a target portion of a substrate; a liquid supplysystem configured to at least partly fill a region between the substrateand the projection system with a liquid; and a saturated gas supplysystem configured to provide substantially saturated gas to a surface ofthe substrate not covered by liquid.
 8. The apparatus according to claim7, further comprising a liquid confinement structure fixed in a planesubstantially perpendicular to an optical axis of the projection systemand configured to contain the liquid, the liquid confinement structurecomprising an extension structure extending substantially radially withrespect to the optical axis from the liquid confinement structure. 9.The apparatus according to claim 8, wherein the extension structure isarranged to cooperate with a vapor sealing projection, forming part of asubstrate table configured to hold the substrate, so as to substantiallycontain the substantially saturated gas.
 10. The apparatus according toclaim 9, wherein the extension structure and the vapor sealingprojection are configured to contain the substantially saturated gas ina region delimited by the substrate table, the substrate, the liquidwhen provided to the region, the liquid confinement structure, theextension structure and the vapor sealing projection.
 11. The apparatusaccording to claim 9, wherein the vapor sealing projection comprises agas seal configured to substantially prevent flow of substantiallysaturated gas through a gap between a surface of the extension structureand the vapor sealing projection.
 12. The apparatus according to claim7, wherein the saturated gas supply system comprises a saturated gaspreparer configured to make substantially saturated gas from the liquid.13. The apparatus according to claim 7, wherein the liquid supply systemis configured to supply liquid to a region covering only a localizedportion of the substrate at any one time.
 14. A lithographic apparatus,comprising: a substrate table configured to hold a substrate to beexposed; a projection system configured to project a patterned radiationbeam onto a target portion on a side of the substrate to be exposed; aliquid supply system configured to at least partly fill a region betweenthe substrate and the projection system with a liquid; a firstconfinement structure fixed in a plane substantially perpendicular to anoptical axis of the projection system and configured to cooperate withthe substrate table in order to restrict the liquid to a region above anupper surface of the substrate table; and a second confinement structurefixed in a plane substantially perpendicular to an optical axis of theprojection system and configured to cooperate with the substrate tablein order to restrict substantially saturated gas to a region above anupper surface of the substrate table, wherein the first and secondconfinement structures and the substrate table are arranged so that aside of the substrate to be exposed is entirely covered withsubstantially saturated gas except for an area covered with liquidduring exposure.
 15. The apparatus according to claim 14, wherein thesubstrate table comprises a vapor sealing projection arranged tocooperate with the second confinement structure so as to substantiallycontain the substantially saturated gas.
 16. The apparatus according toclaim 15, wherein the second confinement structure and the vapor sealingprojection are configured to contain the substantially saturated gas ina region delimited by the substrate table, the substrate, the liquidwhen provided to the region, the first confinement structure, the secondconfinement structure and the vapor sealing projection.
 17. Theapparatus according to claim 15, wherein the vapor sealing projectioncomprises a gas seal configured to substantially prevent flow ofsubstantially saturated gas through a gap between a surface of thesecond confinement structure and the vapor sealing projection.
 18. Theapparatus according to claim 14, wherein the liquid supply system isconfigured to supply liquid to a region covering only a localizedportion of the substrate at any one time.
 19. The apparatus according toclaim 14, further comprising a saturated gas supply system configured toprovide substantially saturated gas to a surface of the substrate notcovered by liquid.
 20. A lithographic apparatus, comprising: a substratetable configured to hold a substrate to be exposed; a projection systemconfigured to project a patterned radiation beam onto a target portionof a substrate; a liquid supply system configured to at least partlyfill a region between the substrate and the projection system with aliquid; a saturated gas supply system configured to providesubstantially saturated gas to a surface of the substrate not covered byliquid; a first confinement structure fixed in a plane substantiallyperpendicular to an optical axis of the projection system and configuredto contain the liquid; and a second confinement structure fixed in aplane substantially perpendicular to an optical axis of the projectionsystem and configured to cooperate with the substrate table in order torestrict substantially saturated gas to a region above an upper surfaceof the substrate table, wherein the first and second confinementstructures and the substrate table are arranged so that a side of thesubstrate to be exposed is entirely covered with substantially saturatedgas except for an area covered with liquid during exposure.
 21. Theapparatus according to claim 20, wherein the substrate table comprises avapor sealing projection arranged to cooperate with the secondconfinement structure so as to substantially contain the substantiallysaturated gas.
 22. The apparatus according to claim 21, wherein thevapor sealing projection comprises a gas seal configured tosubstantially prevent flow of substantially saturated gas through a gapbetween a surface of the second confinement structure and the vaporsealing projection.
 23. A device manufacturing method, comprising: usinga liquid confinement structure, that is fixed in a plane substantiallyperpendicular to an optical axis of a projection system of alithographic apparatus and arranged to cooperate with a substrate tableof the lithographic apparatus holding a substrate, to restrict a liquidto a region above an upper surface of the substrate table and tomaintain a side of the substrate to be exposed entirely immersed in theliquid; and projecting a patterned radiation beam through the liquidonto a target portion of the substrate using the projection system. 24.The method according to claim 23, further comprising: substantiallypreventing the liquid from escaping from a region between the substrateand the projection system using a sealing projection surrounding thesubstrate in a plane substantially perpendicular to the optical axis andconfigured to cooperate with the liquid confinement structure.
 25. Themethod according to claim 24, comprising substantially preventing flowof liquid through a gap between a surface of the liquid confinementstructure and the sealing projection using a gas seal.
 26. The methodaccording to claim 23, further comprising: substantially preventingliquid from escaping from a region between the substrate and theprojection system using a gas seal of the liquid confinement structurecooperating with a sealing zone of the substrate table.
 27. A devicemanufacturing method, comprising: at least partly filling a regionbetween a projection system of a lithographic apparatus and a substratewith a liquid; providing a substantially saturated gas to a surface ofthe substrate not covered by liquid; and projecting a patternedradiation beam through the liquid onto a target portion of the substrateusing the projection system.
 28. The method according to claim 27,further comprising containing the liquid using a liquid confinementstructure fixed in a plane substantially perpendicular to an opticalaxis of the projection system, the liquid confinement structurecomprising an extension structure extending substantially radially withrespect to the optical axis from the liquid confinement structure. 29.The method according to claim 28, comprising substantially containingthe substantially saturated gas using the extension structure incooperation with a vapor sealing projection forming part of a substratetable holding the substrate.
 30. The method according to claim 29,comprising containing the substantially saturated gas in a regiondelimited by the substrate table, the substrate, the liquid whenprovided to the region, the liquid confinement structure, the extensionstructure and the vapor sealing projection.
 31. The method according toclaim 29, comprising substantially preventing flow of substantiallysaturated gas through a gap between a surface of the extension structureand the vapor sealing projection using a gas seal.
 32. The methodaccording to claim 27, further comprising making the substantiallysaturated gas from the liquid.
 33. The method according to claim 27,wherein the liquid covers only a localized portion of the substrate atany one time.
 34. A device manufacturing method, comprising: restrictinga liquid to a region above an upper surface of a substrate table of alithographic apparatus holding a substrate using a first confinementstructure that is fixed in a plane substantially perpendicular to anoptical axis of a projection system of a lithographic apparatus andarranged to cooperate with the substrate table; restrictingsubstantially saturated gas to a region above an upper surface of thesubstrate table using a second confinement structure that is fixed in aplane substantially perpendicular to the optical axis and arranged tocooperate with the substrate table; and projecting a patterned radiationbeam through the liquid onto a target portion of the substrate using theprojection system, wherein the first and second confinement structuresand the substrate table are arranged so that a side of the substrate tobe exposed is entirely covered with the substantially saturated gasexcept for an area covered in the liquid during exposure.
 35. The methodaccording to claim 34, comprising substantially containing thesubstantially saturated gas using a vapor sealing projection of thesubstrate table in cooperation with the second confinement structure.36. The method according to claim 35, comprising substantiallycontaining the substantially saturated gas in a region delimited by thesubstrate table, the substrate, the liquid when provided to the region,the first confinement structure, the second confinement structure andthe vapor sealing projection.
 37. The method according to claim 35,comprising substantially preventing flow of substantially saturated gasthrough a gap between a surface of the second confinement structure andthe vapor sealing projection using a gas seal.
 38. The method accordingto claim 34, wherein the liquid covers only a localized portion of thesubstrate at any one time.
 39. The method according to claim 34, furthercomprising providing a substantially saturated gas to a surface of thesubstrate not covered by liquid.
 40. A device manufacturing method,comprising: restricting a liquid to a region between a projection systemof a lithographic apparatus and a substrate held on a substrate table ofthe lithographic apparatus using a first confinement structure that isfixed in a plane substantially perpendicular to an optical axis of theprojection system; supplying a substantially saturated gas to a surfaceof the substrate not covered by liquid; restricting substantiallysaturated gas to a region above an upper surface of the substrate tableusing a second confinement structure that is fixed in a planesubstantially perpendicular to the optical axis and arranged tocooperate with the substrate table; and projecting a patterned radiationbeam through the liquid onto a target portion of the substrate using theprojection system, wherein the first and second confinement structuresand the substrate table are arranged so that a side of the substrate tobe exposed is entirely covered with the substantially saturated gasexcept for an area covered in the liquid during exposure.
 41. The methodaccording to claim 40, comprising substantially containing thesubstantially saturated gas using a vapor sealing projection of thesubstrate table in cooperation with the second confinement structure.42. The apparatus according to claim 41, comprising substantiallypreventing flow of substantially saturated gas through a gap between asurface of the second confinement structure and the vapor sealingprojection using a gas seal.